diplodia tip blight?

Asked June 10, 2020, 2:24 PM EDT

I have several young Scots pines where the new growth has curled and turned brown. I'm thinking diplodia. I have a Bonide brand Mancozeb with zinc and manganese with 28.7% ethylene bisdithiocabarnate ion, equivalent to 4 parts active ingredient per gallon. The information on the container isn't adequate for me to figure out the dilution needed to spray the pines, so can you give me an idea on quantity of Mancozeb to use per gallon of water, and frequency of spraying if indeed it is diplodia tip blight. Second, is there any point (June 10) of spraying at this point because clearly I've lost this year's growth?

Ingham County Michigan

1 Response

First make sure this is diplodia. There is a white pine weevil that lays its eggs into the top terminal shoots that makes them curl over and it is easy to detect them as they feed just under the bark at the base of expanding shoots. White pine weevil only attack the leaders of the tree and not side shoots. Diplodia is not limited to the top leaders and usually you will see black spores emerging through the needles. Though some concentrations of mancozeb are labeled for use on diplodia, your product is not intended for it. Mancozeb labeled for diplodia has 75% mancozeb and is in a powdered form. I cannot compare one to the other and cannot recommend legally using a product that does not have the intended use on the label. You can call the manufacturer Bonide. There is usually an 800 number on the label for questions such as yours. Bonide Products Inc. 6301 Sutliff Rd. Oriskany, NY 13424 (315) 736-8231